1. Field of the Invention
The present general inventive concept relates to an inkjet printhead and a method of manufacturing the same, and more particularly, to an inkjet printhead that prevents clogging of nozzles and ink spreading during ejection, and a method of manufacturing the inkjet printhead.
2. Description of the Related Art
In general, inkjet printheads eject fine droplets of ink for printing at desired positions on a recording medium to print images of predetermined colors. Inkjet printheads can be classified into two types according to the mechanism of ejecting an ink droplet. One is a thermally-driven type inkjet printhead which generates bubbles in the ink using a heat source to eject ink droplets due to an expansion force of the bubbles. The other one is a piezoelectric type inkjet printhead which ejects ink droplets due to pressure applied to the ink by a deformation of a piezoelectric body. The two types of inkjet printheads eject ink droplets using a constant energy, however the driving devices for the two types of inkjet printheads are different.
FIG. 1 is a sectional view illustrating a general structure of a conventional thermally-driven type inkjet printhead.
Referring to FIG. 1, a conventional thermally-driven inkjet printhead includes a substrate 10, a passage forming layer 20 stacked on the substrate 10, and a nozzle layer 30 formed on the passage forming layer 20. An ink feed hole 51 is formed in the substrate 10. The passage forming layer 20 has an ink chamber 53 to store ink, and a restrictor 52 to connect the ink feed hole 51 and the ink chamber 53. The nozzle layer 30 has a nozzle 54 through which the ink is ejected from the ink chamber 53. Also, the substrate 10 has a heater 41 for heating ink in the ink chamber 53, and an electrode 42 for supplying current to the heater 41.
The ink ejection mechanism of the conventional thermally-driven inkjet printhead having the above-described configuration will now be described. Ink is supplied from an ink reservoir (not illustrated) to the ink chamber 53 through the ink feed hole 51 and the restrictor 52. The ink filled in the ink chamber 53 is heated by the heater 41 consisting of resistive heating elements. The ink boils to form bubbles and the bubbles expand, thereby increasing the pressure of the ink in the ink chamber 53. Accordingly, the ink in the ink chamber 53 is ejected outside the ink chamber 53 through the nozzle 54 in the form of ink droplets.
As an example of a method of fabricating an inkjet printhead, U.S. Patent Application Publication No. 2007/0017894 describes a method of fabricating an inkjet printhead. The method includes forming a plurality of passage walls on a substrate wherein an energy generating device is disposed on the substrate, and stacking covering materials on top surfaces of the passage walls between the passage walls. The method also includes planarizing by polishing upper portions of covering materials until upper portions of the passage walls are exposed, and forming an orifice plate on the upper portions of the polished covering materials and the exposed passage walls.
However, in the conventional method of manufacturing an inkjet printhead described above, a material for forming the nozzles is formed of SU-8 resin, polyfunctional epoxy resin, or the like, and the material also includes an epoxy group or a hydroxyl group as a substitution group.
When nozzles are formed using a compound containing an epoxy, the surface of the nozzles may be deformed due to an instant temperature increase when ink components pass through a heater and react with the epoxy group on the surface of the nozzles. Also, when nozzles are formed using a compound containing a hydroxyl group, the compound containing the hydroxyl group on the surface of the nozzles may react with reactant materials among the ink components and thereby deform the surface of the nozzles, or the compound containing the hydroxyl group may trap metal ions that pass through the nozzles and thus induce accumulation of the metal ions or form a new material in the form of a composite, thereby causing clogging of the nozzles.